This invention relates to a power supply system, and in particular, to a power supply system which has a plurality of power supply devices including a redundant power supply device.
The quantity of electricity which is required to be produced by a power supply system is variable because the number of necessary peripheral devices is variable in accordance with required functions.
An operation of the power supply system is classified into a mode (referred to as a non-redundant operation mode) in which the power supply devices are operated in parallel with the number (referred to as a required power supply device number) of the power supply devices selected in accordance with the required electrical quantity, and a second mode (referred to as a redundant operation mode) in which the number of power supply devices that are operated is larger than the required power supply device number.
During the operation of the power supply system, an abnormality sometimes occurs for the power supply device. In this event, the abnormality must be detected to deal with.
To this end, disclosure has been made about an example of such a power supply system in Japanese Unexamined Patent Publication No. Hei. 5-274061. In the power supply system disclosed in the publication, a plurality of power supply modules (namely, power supply devices) are connected in parallel. Each of the power supply modules has a switching circuit and an abnormal detection circuit. In this case, the switching circuit supplies an output voltage by performing a switching operation while the abnormal detection circuit detects the abnormality of the output voltage which is supplied from the switching circuit.
In the above conventional power supply system, when the abnormality occurs in at least one of the plurality of power supply modules, the abnormal detection circuit which is connected to the abnormal power supply module detects the abnormality and supplies an abnormal signal. The abnormal signal from the abnormal detection circuit is given to the switching circuit. The switching circuit halts the switching operation and turns on a LED to display a abnormal state. When an operator recognizes the lighting of the LED, the operator separates the power supply module having the abnormality which corresponds to the lightening LED from the power supply system.
However, the above conventional system can not recognize whether or not the power supply device having the abnormality corresponds to the required power supply device or the redundant power supply device. Consequently, even when it is unnecessary to halt the total power supply system because the abnormality occurs in only the redundant power supply device, the total power supply system is necessarity halted to separate the power supply device having the abnormality from the power supply system.
To solve this problem, suggestion has been made about the power supply system which can recognize the abnormality of the redundant power supply device in Japanese Patent Application No. Hei. 9-5351. In this system, the total power supply system is not halted when the abnormality of the redundant power supply device is detected.
However, in such a power supply system, when the electrical quantity necessary for the external load apparatus is determined, the required power supply device number in accordance with the electrical quantity furnished the load must be set to the power supply system. Consequently, the operator must operate a switch or a key by opening a checking portion of the power supply system to manually input the required power supply device number. This manual input must be carried out every when the required electrical quantity is changed. This setting operation (namely, manual input) is troublesome for the operator. Further, the operator may erroneously input or set the number.